Microbial Cell Metabolism

glycolysis

• series of rxns w/ end result of glucose oxidized to pyruvate

• major pathway of metabolism for hemoorganotrophs

• sink phase → payoff phase (energy in, more energy out)

major pathway of metabolism for chemoorganotrophs

glycolysis

are stage 1 (investment) or stage 2 (payoff) redox rxns?

2

glycolysis stage 2 are redox rxns lead to _________

pyruvate

is glycolysis a balanced redox rxn? why/why not?

no

• generates NADH, lacks an e- acceptor to regenerate the NAD+

how is glycolysis balanced out?

it is coupled to other mechanisms such as fermentation, citric acid cycle, & respiration

what is required to produce 2 ATP via glycolysis?

• 1 glucose

• 2 pyruvate

• 2 NADH

citric acid cycle

• pyruvate is oxidized to CO2

• not balanced

• net result of 1 turn = 1 ATP, 4 NADH, 1 FADH2

net result of 1 turn of the citric acid cycle

• 1 ATP

• 4 NADH

• 1 FADH2

when glycolysis is coupled to TCA, we get…

• 4 ATP

• 10 NADH

• 2 FADH2

where does electron transport (& hydrogen transport) occur?

• cytoplasm of bacteria

• inner membrane of mitochondria

list enzymes that participate in converting NADH & FADH2 back to NAD+ and FAD

• NADH dehydrogenase

• flavoproteins

• iron-sulfur cluster proteins

• cytochromes

dehydrogenases

bind NADH and release 2e- and 2H+ across the membrane

flavoproteins

contain riboflavin derivative as a cofactor & is reduced as it accepts 2e- and 2H+

cytochromes

pass e- via reduction and oxidation of an iron co-factor or heme group

ETC generates an __________ gradient across the cytoplasmic membrane

electro-chemical

proteins of the ETC are arranged in complexes ________

I-IV

in aerobic respiration, the terminal electron acceptor is _______

oxygen

• complex IV

the ETC progresses from a gradient of increasingly ___________ reduction potentials

positive

complex I results in ___ H+ across the cell (this is where NADH is converted back to NAD+)

4

complexes I-III are linked by _______

quinone pool

quinones

• small, hydrophobic redox molc w/o protein

• move about the membrane & aren’t bound

• transfer e- b/w steps in the ETC (not protons)

• Q-cycle

oxidative phosphorylation

generation of ATP from ADP & inorganic phosphate

• driven by respiration

• driven by PMF

ATP synthase

inner membrane protein that binds H+ and transfers it into the cytoplasm

ATP synthase has a similar motor to that of the __________

flagella motor protein

what drives the synthesis of ATP?

• mechanical energy (rotation)

• ~3.3 H+

net ATP gain when glucose is completely oxidized

~30-38

vast majority of ATP is generated in…

oxididative phosphorylation

the number of ATPs able to be generated via oxidative phosphorylation is directy related to …

how strong the PMF is

• how many H+ ions are on the outside vs inside of the cytosol

is ATP synthase reversible? (can it turn ATP to ADP?)

yes → ADP can be generated when H+ is higher inside

respiration means there is a ________ and a ___ is generated leading to phosphorylation

terminal electron acceptor / PMF

does fermentation lead to generation of a PMF?

no

does fermentation require a terminal e- acceptor?

no

what happens when components of the ETC are missing?

• weaker PMF

• decreased ATP production

• slower growth

does anaerobic respiration yield more or less ATP?

less

• fewer H+ ions

do aerobes or anaerobes grow faster? why?

aerobes

• produce more ATP

is fermentation an aerobic or anaerobic process?

anaerobic

purpose of fermentation

produces small amt of ATP to maintain redox balance

fermentation is a ________ event

substrate-level phosphorylation

ferementation allows ______ to be recycled into ______

NADH / NAD+